In general, desalination and purification of saline or polluted water using buoyant gas hydrates is known in the art. According to this approach to water desalination or purification, a gas or mixture of gases which spontaneously forms buoyant gas hydrate when mixed with water at sufficiently high depth-induced pressures and/or sufficiently low temperatures is mixed with water to be treated at the relatively deep base of a treatment column. Because the hydrate is positively buoyant, it rises though the column into warmer water and lower pressures. As the hydrate rises, it becomes unstable and disassociates into pure water and the hydrate-forming gas or gas mixture. The purified water is then extracted and the gas is processed and reused for subsequent cycles of hydrate formation. Suitable gases include, among others, methane, ethane, propane, butane, and mixtures thereof.
According to the series of prior patents and applications referenced above to which this application is related, hydrate-based desalination may be conducted in a hydrate fractionation shaft or column constructed in land, the depth of the column being sufficient for the weight of the water at the base of the column to generate the requisite hydrate-forming pressure. Alternatively, hydrate-based desalination may be conducted in a shaft located in an open-ocean environment, as is disclosed, for example, in U.S. Pat. Nos. 3,027,320 and 5,873,262. The present invention may be employed in connection with either in-land-shaft-based desalination (or other water purification) or open ocean-based desalination (or other purification).